It is well known that a chlorinated vinyl polymer referred to as chlorinated polyvinyl chloride, hereinafter CPVC, has excellent high temperature performance characteristics, among other desirable physical properties. Typically, commercial CPVC has in excess of about 57 percent by weight (% by weight) bound chlorine, and is most conveniently prepared by the chlorination of polyvinyl chloride as described in U.S. Pat. Nos. 2,996,489; 3,100,762; 3,334,077; 3,334,078; 3,506,637; 3,534,013; 3,591,571; 4,049,517; 4,350,798; 4,377,459; 4,412,898; and 4,459,387 inter alia.
The term CPVC is used herein to define a chlorinated vinyl chloride polymer having in excess of about 57% by weight bound chlorine.
Chlorinated PVC (CPVC) has become an important specialty polymer due to its relatively low cost, high glass transition temperature, high heat distortion temperature, outstanding flame and smoke properties, chemical inertness and low sensitivity to hydrocarbon feed stock costs. The glass transition temperature of CPVC generally increases as the percentage of chlorine increases. However, a well known undersirable characteristic of CPVC resin is that it inherently has low impact properties, a characteristic which is also common to vinyl chloride homopolymers. Also, as the chlorine content increases, the CPVC resin becomes more difficult to melt process, and also becomes more brittle.
The poor melt processability of CPVC resins is exemplified by milling CPVC on a roll mill which results in high torque and high temperatures as well as decomposition of the CPVC. Softening additives or plasticizers have been added to CPVC in order to improve its processability. Although its processability is somewhat improved, these additives produce undesirable effects. Some of the more significant detrimental effects produced by inclusion of these softening or plasticizer additives are lower heat distortion temperatures, softness and weakness in terms of lower tensile strength, and less desirable chemical properties than that exhibited by CPVC alone. These negative attributes of the additives on CPVC limit usefulness of the modified CPVC in the manufacture of rigid plastic articles.
The burgeoning demand for CPVC pipes, vessels, valve bodies and fittings, and the fact that an impact-deficient CPVC matrix can be improved by compounding and alloying it with other polymers, has instigated concerted efforts to develop better impact modified CPVC compositions having increased heat distortion temperatures, and increased ease of melt-processing. Most of these efforts have been channeled toward rigid CPVC applications where acceptable impact strength and dimensional stability under heat are critical. Such applications include the manufacture of exterior structural products, rigid panels, pipe and conduit, injection-molded and thermoformed industrial parts, appliance housing, and various types of containers both large and small.
U.S. Pat. No. 3,882,192 to Elghani, et al relates to molding compositions consisting of from 5 to 95 parts by weight of a polycarbonate, from 5 to 95 parts by weight of a vinyl chloride polymer, and from 5 to 95 parts by weight of an ABS graft polymer, a styrene/maleic anhydride copolymer or an ethylene/vinyl acetate copolymer. Molding compositions are made by solution casting, that is by seperately dissolving each component in a suitable inert organic solvent. The three components can then be mixed together and the molding composition isolated from the solutions by precipitation with non-solvents or by removal of the solvents by distillation. Processing of the molding compositions is carried out at a temperature of about 250.degree. C. In addition to high processing temperatures, which is too high for processing of high chlorine CPVC, no mention is made of the utilization of an ethylene-based functional polymer.
U.S. Pat. Nos. 4,105,711; 4,239,361; and 4,515,925 while relating to polymer mixtures containing polycarbonate, do not utilize any ethylene-based functional polymer.
At present, no entirely satisfactory means is available for improving properties such as impact strength, heat distortion temperatures, improved ease of melt processing of chlorinated PVC resins, or any combination thereof.
Since PVC processes easily and CPVC does not, since CPVC has heat resistance but PVC does not, and furthermore, since CPVC has a high melt viscosity but PVC does not, it should be apparent that CPVC and PVC are different materials and that PVC prior art is not analogous to patentability issues relating to CPVC.